PERTHES’ DISEASE IN CHILDREN

Perthes’ disease is avascular necrosis of the femoral head of unknown aetiology. The interruption of the blood supply to the femoral head results in collapse, fragmentation and progressive deformity of the hip joint. It affects the age groups 4-10 years. Males are more frequently affected than females by 4:1 and it is bilateral in 25% of cases.

A child suffering from this condition usually presents with hip pain or a limp. However, in 30% of cases the pain may initially be referred to the thigh or the knee. This could on occasions result in missed or delayed diagnosis, especially if the hips are not radiographed routinely in a child with knee or thigh pain.

Perthes’ disease is recognised to undergo a number of well defined radiological stages i.e. necrosis, fragmentation, healing and remodelling stages.

The Natural History of untreated Perthes’ disease is eventual healing and revascularisation of the necrotic femoral head within 2-3 years. In 75% of the cases the healing process results in a round congruent hip joint with good to excellent outcome in the long-term. In these cases no treatment other than careful follow-up is necessary.

In contrast in 25% of untreated cases this condition results in severe deformity of the hip joint. In these cases operative intervention may be required to improve the outcome.

It is important to note that from onset of Perthes’ disease i.e. necrosis stage until the lesion heals (healing stage) it may take up to 2-3 years. Regardless of the prognosis, the affected child is expected to experience intermittent pain and limping during this period until healing stage is reached.

Treatment is not required for children with good prognosis. Good prognosis is indicated by the following clinical features:
• Age less than 6 years at the onset of symptoms.
• Less than 50% of head involvement.
• No stiffness or shortening on examination.

On the other hand bad prognosis is indicated by the following clinical findings:
• Age more than 7 years at the onset of symptoms.
• More than 50% of head involvement.
• Significant stiffness or shortening on examination.

In poor prognosis group operative intervention could improve the outcome. In general there are 2 class of operations available to treat Perthes’s disease: i) Containment, ii) Corrective Osteotomy.

Containment is most suitable for cases within the necrosis or fragmentation stages. During these early stages the femoral head remains malleable and the aim is to contain the femoral head deep within the acetabulum until healing occurs. The acetabulum which is hemispherical in shape helps to remodel the femoral head into a round shape. Varus femoral or pelvic osteotomy are the operations generally done for containment.

Corrective osteotomy is more suitable for cases that have entered the healing or remodelling stages. in these stages the femoral head deformity is unlikely to remodel by containment . Corrective osteotomy aims to address residual problems such limb shortening or limited abduction in the hip. the most popular type of osteotomy in this situation is usually a valgus lengthening osteotomy.

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